THE EFFECTS OF HIGH-INTENSITY INTERVAL
TRAINING
IN THE AEROBIC PERFORMANCE OF YOUNG SOCCER PLAYERS IN COMPETITIVE
SEASON

Theophilos PILIANIDIS1,
Nikolaos MANTZOURANIS1,Kostas KYRIKLIDIS1,

Andreas ZAFIRIDIS2, Spyros KELLIS2

1. Department of
Physical Education and Sport Science, Democritus University of
Thrace, Greece

2. Department of
Physical Education and Sport Science, Aristotle University of
Thessaloniki, Greece

Abstract

The aim of this study was to evaluate the effects
of the short-term and extremely short-term interval training
protocols on the aerobic performance in young soccer players. Thirty
six (n=36) amateur players aged 16.2±1.1yrs participated in
the present study. After the baseline laboratory evaluation (VΟ2max,
vVΟ2max,
RE, vAT), the subjects were subdivided in 3
groups: the short-term group [A(15s:15s)], the extremely short-term
group [B(6s:30s)] and the control group (C). After the completion of
the 10-week research protocols, the players’ aerobic
performance was reevaluated. The repeated
measures analysis of variance (ANOVA) was applied in order to
evaluate the interactions of the 10-week interval training protocols
on the players’ aerobic capacity. The results showed that the
training groups presented a significant improvement in the VO2max
(9.63% & 7.4%) and the vVO2max
(5.8% & 5.35%) while the control group did not improve. In
addition, the running economy (RE) did not improve significantly in
the players of the interval training groups while the analysis
of variance revealed that the intervention protocols did not affect
the players’ velocity in the anaerobic threshold (vAT).
Conclusively, the interval training protocols of 15s:15s and 6s:30s
which were applied in a time period of 10 weeks contributed to the
increase of both the VO2max
and the vVO2max
in young soccer players.

Soccer is one of
the most popular team sports in the world and millions of athletes
desire to occupy themselves with it. The contemporary way of soccer
playing requires from the athletes to maximize their performance
which is consisted by factors such as the physical conditioning, the
technical tasks, the team tactics and the psychological parameters
(Ekblom,
1986; Balsom, 1994).
Specifically in physical conditioning, the intensity, the volume and
the rest periods are important components of the soccer annual
training plan both in top-level as well as in amateur players(Wenger & Bell, 1986).
Furthermore, it is significant for the soccer coaches to simulate the
physical conditioning training to the high-intensity phases or the
recovery periods of the match. In addition, it could be beneficial
for the coaching procedures to work simultaneously on the player’s
technique as well as on the team tactics during the conditioning
training especially in top-level soccer players, (Reilly,
2005).

In the late 1990s the interval training programs
presented the short-term high intensity protocols which were applied
for the improvement of aerobic and anaerobic capacity of the soccer
players. An improvement in the players’ VO2max
was recorded for the first time in a 6-week program of high intensity
bouts and short durations of rest intervals (Tabata
et al., 1997). Similarly, in a 9-week
interval training program with 4 repetitions of high intensity runs
of 30s duration, an improvement was presented in both aerobic and
anaerobic performance in top-level soccer players (Helgerud,
Høydal & Wang 2007). Additionally, a 2
week training program of 15s maximal intensity runs and 45s rest
intervals recorded an improvement in enzymatic activities of both
aerobic and anaerobic metabolism in professional soccer players
(Casajus, 2001).

In the 2000s a number of studies confirmed that
the high intensity interval training affects positively the soccer
players’ aerobic performance. During the competitive season,
additionally to the normal team program, a high intensity 10-week
interval training protocol increased the players’ aerobic
capacity resulting in an important improvement of the overall team
competitive performance (Dupont, Akakpo & Berthoin,
2004). Furthermore, the interval training was reported to improve the
running fatigue resistance as well as the players’
speed-endurance in soccer because of its brief rest intervals (Hoff
et al., 2002). In recent studies, a 7-week interval training program
recorded an improvement of 6% to 7% in young soccer players’
VO2max
(Impellizeri et al.,2006; Ferrari et al.,
2008). Through the time, although a great
number of studies have assessed the effects of the interval training
in the soccer players’ competitive performance, very few
studies have compared the interval training in young athletes’
performance during the competitive season. Therefore, the aim of the
present study was to evaluate the effects of the two interval
training protocols (short-term & extremely short-term duration)
on the aerobic capacity of the young soccer players during the
competitive season.

Materials
and Methods

Participants

Thirty six (n=36) male soccer players from a
Football Club were recruited for the study. Theirmeanageandtrainingexperiencewere 16.2±1.1yrs and 4±1.2yrs
respectively, while the goalkeepers were excluded from the study.The selection of the participants
for this study was based on the criteria of: i) the training
experience (more than 2 years), ii) the absence of any drug treatment
and iii) the frequency of training (4 sessions per-week). All
participants completed a short questionnaire on their medical history
and it was confirmed that they had no previous history of lower limb
injury. Parents were informed about the research and they were asked
to complete a written informed consent prior to their children’s
participation.The study was performed
according to the rules of the Ethics Committee of the Democritus
University of Thrace.

TestingProcedures

The laboratory measurements were applied to the
participants two days before and two days after the training
intervention, at the same time of the day (15:00–20:00)
and under similar ambient conditions (22o–23oC)
and relative humidity (35–40%).
A motorized treadmill (H-p Cosmos)
was used for the estimation of the players’ VΟ2max
while the expired gas was analyzed with a breath-by-breath automated
gas-analysis system (Quark PFT Ergo, Cosmed). Before each test flow,
the volume and the gases were calibrated according to the
manufacturer’s recommendations. During the incremental running
test the VO2,
VCO2,
VE and RER were estimated every 15s. After the baseline assessment
completion, the players were divided in three equal groups:
Α [interval training 15s:15s (120%
vVO2max)], Β
[interval training 6s:30s (145% vVO2max)]
and C [control group]. The criteria for the groups’ subdivision
were the initial ergo spirometer values so that the participants of
the 3 groups would be equal in VO2max
and vVO2max.
After the 10 weeks of the interval
training intervention the laboratory measurements were repeated in
order to evaluate the adaptations of the training in the
participants’ aerobic capacity. In
the amount of the participants in this study, the obtained
vVO2max from
the baseline laboratory measurement ranged between15 and 17km.h-1.
The shuttle running distances which were covered by the interval
training groups (Α:15s:15s & Β
6s:30s) in relation to their vVO2max
are presented in figure
1.

vVO2max:15km/h

15s running in 120% vVO2max

75m

vVO2max: 16km/h

15s running in 120% vVO2max

80m

vVO2max:17km/h

15s running in 120% vVO2max

85m

vVO2max:15km/h

6s running in 145% vVO2max

36.2m

vVO2max:16km/h

6s running in 145% vVO2max

38.6m

vVO2max:17km/h

6s running in 145% vVO2max

41.6m

Research Protocol

During the 10 week research, the players of all
groups participated in the soccer team normal training program which
consisted of technical and tactical skills, high intensity games as
well as the official game of the team every Sunday. The players of
the interval training groups (A & B) performed their programs
every Monday and Thursday complementary to the normal training of
their team, while on Wednesdays the players of all groups trained
with equal training intensities. The interval training consisted of 3
set x 6-8 runs with a passive recovery of 3min between the running
bouts, while the players of the control group were trained only with
the normal weekly training program of the team. After the first 3
weeks of the interval intervention the number of bouts gradually
increased from 6 to 8 repetitions per set from the 4th
to the 10th
week. All training sessions were conducted
outdoors on a grass pitch and all players wore soccer shoes. The A
and B groups’ interval training programs are presented in Table
1.

Table
1.The
10-week-training programs which were applied in
the players in
Groups
A and B.

Training
parameters

Group A

Group B

Number of soccer training/week

3+1

3+1

Number of interval training programs/week

2

2

Duration of interval bouts

15s

6s

Restingperiods

15s

30s

Running intensity

120% vVO2max

145% vVO2max

Rest type

passive

passive

Bouts per training session

18-24

18-24

Set recovery

3min

3min

Duration of interval training

4:30–6min

2-2:30min

Duration of resting interval

10:30-12min

15-18min

Duration of interval training programs

17±1min

18±1min

Statistical analysis

Descriptive statistics with exploration and cross-tabulation were
firstly applied for all the continuous variables (mean±SD).The scatterplots were used in order to determine
whether a linear model is reasonable for the variables of players’
performance in relations to the research
protocols. The data normality was confirmed by using the
Kolmogorov-Smirnov test, while the equality of
variances in all testing variables was assessed by using the Levene’s
Test.The
statistical design for the measured variables of this study was based
on the Analysis of Variance (ANOVA). The interaction among the
evaluated parameters in each group was assessed by analysing the
dependent factor “measurement” (pre-post) with the
independent factor “Group”
[(A:15s:15s)-(B:6s:30s)-(Control Group)].The
Bonferroni correction (post hoc comparisons) was applied in
order to identify the inter groups statistically significant
differences in the evaluated variables of this study. The acceptable
level of significance was set at 0.05. All statistical analyses were
carried out by employing the PASW-SPSS software, version 18.0 for
Windows (SPSS, Inc., Chicago, IL).

Results

The statistical analysis showed that the VO2max
and the vVO2max
were significantly affected only in the players of the interval
training groups, while no differences were recorded in the VO2max
and the vVO2max
between the intervention groups.
In addition, the interaction of the variables “measurement x
training intervention” was significant only in the VO2max
of the participants of the interval training groups (A) 15s:15s and
(B) 6s:30s (F1.33=47.66,
p<0.05), while the pre and post vVO2max
did not differ significantly in the
interval training groups (F1.33=1.22,
p=0.31). The post hoc
Bonferroni comparisons showed that in the interval training groupsthe players improved significantly
in both post VO2max
[(A:9.63%) & (B:7.4%)] and vVO2max
[(A:5.8%) & (B:5.35%)]. Finally, the Control Group did not
present any significant differences from the baseline to the final
laboratorymeasurement as far as the VO2max
and the vVO2maxis concerned.

The running economy (RE) which is defined as the
oxygen consumption (ml.kg-1.min-1)
at the 70% of the vVO2max,
was not significantly improved in the players
of the interval training groups.
From the results it is shown that there were no interactions in the
players’ RE after the 10-week training intervention. In spite
of the fact that the oxygen consumption of the players who
participated in the interval training groups decreased [(A:2.8%) &
(B:1.7%)], the mean RE of the players marginally increased with no
statistical significance (F1.33=0.97,
p=0.76). Furthermore, no differences were found in the oxygen
consumption and in the RE of the players in the Control Group. In
addition, the analysis of variance revealed that the training
protocols did not significantly affect the players’ vAT.
However, the participants of the group A (15s:15s)
presented an increase of 7.8% in the vAT
while the players in the group B (6s:30s)
improved their vAT as high as 6.1%.
Finally, in the participants of the Control Group a marginal increase
(2.5%) in the vAT was recorded. The
pre and post research protocol measurements of the players’
aerobic capacity are illustrated in table 2.

Table 2.VO2max,
vVO2max
and RE measuring parameters in all group studied players, (mean±SD).

Interval Group (A)

Interval Group (B)

Control Group (C)

(15s:15s)

(6s:30s)

Parameters

Evaluation

mean

SD

mean

SD

mean

SD

Pre-train

49.98

5.28

50.07

3.59

49.67

1.02

VO2max (ml.kg-1.min-1)

Post-train

55.31

5.05

54.06

2.98

50.42

0.86

Pre-train

14.21

1.03

14.00

1.29

13.88

0.21

vVO2max (km.h-1)

Post-train

15.08

1.11

14.79

1.43

14.17

0.23

Pre-train

38.66

1.92

39.37

2.67

39.15

2.74

RE (ml.kg-1.min-1)

Post-train

37.61

1.70

38.71

1.28

38.80

3.21

Pre-train

9.83

1.14

9.67

1.02

9.55

0.11

vAT (km.h-1)

Post-train

10.67

1.10

10.29

1.02

9.80

0.11

Discussion

The results of the present study are in agreement
with a similar design research which showed that the players of the
intervention groups improved their VO2max.
This confirms that the high intensity of the interval training
increases linearly the VO2max
as a result of the greater mitochondrial respiratory capacity
(Brooks, Fahey & White, 1996). In
addition, the soccer players of the training group A (15s:15s)
presented a greater improvement in both the VO2max
and the vVO2max.in
comparison to those of the training group B (6s:30s). The
above findings are in conjunction with studies which agree on the
fact that the interval training with intensities of the 120% of the
vVO2max
is more effective for the increase of the VO2max
compared to the interval training with exercise intensities of 145%
of the vVO2max which
are mostly focused on the anaerobic capacity improvement of the
soccer players (Franch, Madsen & Djurhuus, 1998; Billat,
2001). Furthermore, another explanation for the greater improvement
of the VO2max
of the A group players (15s:15s) compared to the players of group B
(6s:30s) is that the players of the group A had the benefit of the
aerobic adaptations from this interval program even in the recovery
periods of this type of training (Dupont,
Akakpo & Berthoin, 2004).

In addition, the results of this study showed that both interval
training programs improved the participants’ vVO2max
as measured during the final aerobic performance laboratory
measurement. Specifically, the increases of the soccer players’
vVO2max
were 5.8% for the 15s:15s
group (A) and 5.35% for the 6s:30s group (B). The above findings
regarding the rate of the vVO2max
improvement are better than
other studies which presented that the level of increase of the
vVO2max ranged
from3% to 3.8% (Billat,
Flechet, Petit, Muriaux & Koralsztein, 1999; Smith, McNaughton
&
Marshall, 1999). Moreover, the 10- week duration of the interval
training intervention confirmed that the program of the 15s:15s group
improved the adolescent soccer players’ vVO2max
(Lacour et al., 1991). Finally, the results of this study confirm
that the rate of the athletes’ improvement in the vVO2max
is greater when the VO2max
in young sport participants ranges
between 45 and 55ml.kg-1.min-1
(Dupont, Blondel, Lensel & Berthoin, 2002;Ferrari-Bravoetal., 2008).

Moreover, the current bibliography for the interpretation of the
running economy is still in conflict mainly with the duration of the
training programs. The marginal improvement of the running economy of
the participants in the intervention groups is in agreement with the
studies which denoted that the 6-week training could positively
affect the running economy in moderate trained athletes (Bailey
& Pate, 1991; Sperlich, 2011). In contrary,
the majority of the relevant studies are in agreement with this study
which presented that the running economy of the athletes improves in
a time period of 13 to 104-weeks(Andersonetal., 1996; Bishop, Girard,
Mendez-Villanueva, 2011).

In addition, the increases of the post
intervention measurement in the vAT in both
interval training groups players (A:7.8% & B:6.1%) are
interpreted by the literature, which reports that the intensities of
the interval training above the anaerobic threshold and close to the
vVO2max
improve the athletes’ anaerobic threshold (Burke, Thayer
&Belcamino 1994; Impellizzeri
et al., 2008). However, the lack of significance in the above
increase in the vAT in the two training groups
makes the researchers unable to justify why the interval training
programs (15s:15s & 6s:30s) are beneficial for the anaerobic
threshold improvement of the soccer players.

In summary, the findings of the current study showed that the short
bouts and the extremely short bouts of the interval training seem to
improve the VO2max
and increase the vVO2max
in young soccer players. More specifically, the 15s:15s
in relation to the 6s:30s interval training during the competitive
season has a potential to the physiological adaptations which are
related to an increase on the aerobic metabolism in young soccer
players. Future research is required for the evaluation of the
metabolic, hormonal or psychological factors which could provide
valuable information to the coach regarding the team training plan in
order to enhance the competitive performance in developmental age and
professional soccer players.